基于复合势垒层的凹槽二次外延p型栅常关型GaN基HEMT研究

基于p型栅的常关型GaN基高电子迁移率晶体管（HEMT）具有独特优势和重要应用前景。常规方法采用基于单势垒层的异质结构，通过干法刻蚀形成p型栅，难以实现器件常关性能与导通特性的同时优化。在前期工作基础上，本项目提出基于双Al组分复合势垒层的新型异质结构，采用自主研发的含氧等离子体刻蚀自终止技术，实现凹槽栅的可控制备，进一步通过整面二次外延生长p型层与非栅极区域p型层的选择性刻蚀相结合的方案，构筑兼具高关态性能、高导通特性的器件结构，研制高性能常关型HEMT。具体围绕复合势垒层中的极化与能带结构调控、凹槽区域p型层二次外延生长动力学、Mg掺杂及缺陷/界面态与器件性能的关联规律等关键科学问题，重点研究复合势垒层的异质结构设计与生长、高质量p型栅的凹槽二次外延及其对器件性能的影响机制等，目标实现兼具高阈值电压、大栅压摆幅、低导通电阻、及优良动态特性的常关型GaN基HEMT。

GaN-based normally-off high-electron-mobility transistor (HEMT) with a p-type gate has emerged as a promising candidate for applications in power electronics. However, it is challenging to achieve a high threshold voltage and a low on-resistance simultaneously with a conventional method, in which a single AlGaN barrier is used in the heterostructure and the p-GaN gate is formed by dry etching. On the basis of our previous work, we propose a novel heterostructure with double AlGaN barriers combined with a precise and uniform fabrication of recessed gates through a self-terminated etching process. Furthermore, p-GaN planar regrowth followed by a selective etching of the non-gate region p-GaN will be adopted for the construction of high-performance normally-off HEMTs. This project will focus on the design and growth of the composite heterostructure with an engineered control of polarization and band structure, the regrowth dynamics of p-GaN layer in the recessed region, and their influences on the device performance. The goal of this project is to develop high-performance normally-off GaN-based HEMTs featuring a high threshold voltage, a large gate swing, a low on-resistance, and great dynamic characteristics.